Generally, golf balls have been classified as wound balls or solid balls. Wound balls are generally constructed from a liquid or solid center surrounded by tensioned elastomeric material. Wound balls are performance golf balls, and have a good resiliency, spin characteristics and feel when struck by a golf club. However, wound balls are generally more difficult to manufacture than solid golf balls.
Early solid golf balls were generally two piece balls, i.e., comprising a core and a cover. The primary purpose of the core is to be the “spring” of the ball or the principal source of resiliency. The cover protects the core and improves the spin characteristics of the ball. More recently developed solid balls comprise a core, a mantle layer and a cover to improve the playing characteristics of the balls.
Solid balls are typically made with a single-solid core, usually made of a cross-linked polybutadiene or other rubber, which is encased by a cover. These balls are typically the least expensive to manufacture as the number of components is low and these components can be manufactured by relatively quick, automated molding techniques.
The prior art also discloses golf balls that have been designed to provide particular playing characteristics. These characteristics include the initial velocity and spin of the golf ball, which can be optimized for various types of players. For instance, certain players prefer a ball that has a high spin rate in order to control and stop the golf ball. Other players prefer a ball that has a low spin rate and high resiliency to maximize distance. Generally, a golf ball having a hard core and a soft cover will have a high spin rate. Conversely, a golf ball having a hard cover and a soft core will have a low spin rate. Golf balls having a hard core and a hard cover generally have very high resiliency for distance, but have a hard feel and are difficult to control around the greens.
The prior art also discloses golf balls with multi-layered core, such as United States patent application Ser. No. 2002/0019268, which discloses a six-layer core with an inner core layer having a low modulus of elasticity and an outer core layer having a high modulus of elasticity. Golf balls with two-layer core are also known, such as U.S. Pat. Nos. 6,245,859 B1, 6,213,895 B1 and 6,057,403, among others. Similarly, golf balls with three-layer core are disclosed in U.S. Pat. Nos. 5,772,531 and 5,743,816. However, none of these references discloses multi-layered golf ball core with predetermined thickness ratio among all the core layers.